(Applicant's Abstract) Rationale. The SCOR program is highly dependent upon the generation and maintenance of transgenic mice for the study of lung development and disease. This Core is designed to take advantage of established expertise in the generation of the transgenic mice used for the study of lung disease and for gene ablation studies that will be required for the present SCOR projects. Likewise, maintenance of pathogen-free, wild-type and transgenic lines will be critical for supplying genotyped mice for the various projects. This Core will both generate new transgenic lines and gene targeted mice, as well as maintain breeding and genotype analysis for the transgenic mice as required for the individual projects and investigators. This Core will: 1. provide animal husbandry, breeding, tail clip, Southern blot, PCR analysis for the mouse lines required for the SCOR projects. 2. generate all new transgenic lines described in the protocols by pronuclear injection and blastocyst injection for gene targeting. 3. Facilitate maintenance, breeding and surveillance of the transgenic animal models. 4. Monitor and facilitate oxygen exposure chambers and viral exposure protocols. 5. Develop new transgenic models for site-specific conditional expression of transgenes in the lung. The animals will be maintained in filtered-barrier caging in a pathogen-free facility at the Children?s Hospital Research Foundation under the direction of Gary Keller, D.V.M. This animal care program includes the use of sentinel mice and careful ongoing serological and pathologic surveillance for identification of pathogens. Such surveillance will be critical in the evaluation of lung disease in our various transgenic models and be necessary for the interpretation of genetic vs. environmental effects on lung development and repair following injury.